3r^2+8r+15=

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Solution for 3r^2+8r+15= equation:


Simplifying
3r2 + 8r + 15 = 0

Reorder the terms:
15 + 8r + 3r2 = 0

Solving
15 + 8r + 3r2 = 0

Solving for variable 'r'.

Begin completing the square.  Divide all terms by
3 the coefficient of the squared term: 

Divide each side by '3'.
5 + 2.666666667r + r2 = 0

Move the constant term to the right:

Add '-5' to each side of the equation.
5 + 2.666666667r + -5 + r2 = 0 + -5

Reorder the terms:
5 + -5 + 2.666666667r + r2 = 0 + -5

Combine like terms: 5 + -5 = 0
0 + 2.666666667r + r2 = 0 + -5
2.666666667r + r2 = 0 + -5

Combine like terms: 0 + -5 = -5
2.666666667r + r2 = -5

The r term is 2.666666667r.  Take half its coefficient (1.333333334).
Square it (1.777777780) and add it to both sides.

Add '1.777777780' to each side of the equation.
2.666666667r + 1.777777780 + r2 = -5 + 1.777777780

Reorder the terms:
1.777777780 + 2.666666667r + r2 = -5 + 1.777777780

Combine like terms: -5 + 1.777777780 = -3.22222222
1.777777780 + 2.666666667r + r2 = -3.22222222

Factor a perfect square on the left side:
(r + 1.333333334)(r + 1.333333334) = -3.22222222

Can't calculate square root of the right side.

The solution to this equation could not be determined.

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